Motorcycle including brake-by-wire system with flexibly supported pressure-generating unit

ABSTRACT

In a brake system for a motorcycle in which the operation of a pressure-regulating unit interposed between fluid pressure-generating unit and a wheel brake so as to regulate an output fluid pressure of the fluid pressure-generating unit and to apply the regulated fluid pressure to the wheel brake is controlled by a control unit on the basis of a value detected by operating amount detector for detecting an operating amount of a brake operating element, to arrange the fluid pressure-generating unit in a location which is close to the pressure control unit disposed on the rear side of an engine body and in which an installation space is easy to secure. The fluid pressure-generating unit, laid out in plan view between a left-right pair of seat rails which constitute a part of a body frame and which support a riders&#39; seat, is supported by the seat rails.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2008-091950, filed on Mar. 31, 2008. The entire subject matter of this priority document, including specification claims and drawings, is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motorcycle including an operating amount detector for detecting an operating amount of a brake operating element, fluid pressure-generating unit capable of generating a fluid pressure independently of an operation of the brake operating element, a pressure-regulating unit interposed between the fluid pressure-generating unit and a wheel brake so as to regulate an output fluid pressure of the fluid pressure-generating unit and to apply the regulated fluid pressure to the wheel brake, and a control unit for controlling the operation of the pressure-regulating unit on the basis of a value detected by the operating amount detector, the pressure-regulating unit being arranged on the rear side of an engine body mounted on a body frame.

2. Description of the Background Art

A configuration in which fluid pressure-generating unit and a pressure-regulating unit are mounted to a body frame on the rear side of an engine mounted on a motorcycle has been known, as described in the Japanese Patent Publication Nos. Sho 63-17662 and Hei 7-88158.

Meanwhile, in the configuration as disclosed in the Japanese Patent Publication Nos. Sho 63-17662 and Hei 7-88158, the fluid pressure-generating unit and the pressure-regulating unit are unitized. However, the fluid pressure-generating unit and the pressure-regulating unit may be arranged separately. In that case, it is desirable that the fluid pressure-generating unit be disposed at a position which is comparatively close to the pressure-regulating unit and at which an installation space is easy to secure.

The present invention has been made in consideration of the above-mentioned circumstances. Accordingly, it is an object of the present invention to provide a motorcycle in which fluid pressure-generating unit is arranged in a location which is close to a pressure-regulating unit disposed on the rear side of an engine body and in which an installation space is easy to secure.

SUMMARY OF THE INVENTION

In order to achieve the above objects, In order to attain the above object, the invention according to claim 1 resides in a motorcycle including operating amount detector for detecting an operating amount of a brake operating element, fluid pressure-generating unit capable of generating a fluid pressure independently from an operation of the brake operating element, a pressure-regulating unit interposed between the fluid pressure-generating unit and a wheel brake so as to regulate an output fluid pressure of the fluid pressure-generating unit and to apply the regulated fluid pressure to the wheel brake, and a control unit for controlling the operation of the pressure-regulating unit on the basis of a value detected by the operating amount detector, the pressure-regulating unit being disposed on the rear side of an engine body mounted on a body frame, characterized in that the fluid pressure-generating unit, laid out in plan view between a left-right pair of seat rails which constitute a part of the body frame and which support a riders' seat, is supported by the seat rails.

The invention according to claim 2 is characterized in that, in addition to the configuration of the invention according to claim 1, the fluid pressure-generating unit is floatingly supported, through an elastic member, by a first support member which is attached to one of both the seat rails and by a crossmember which connects both the seat rails to each other.

The invention according to claim 3 is characterized in that, in addition to the configuration of the invention according to claim 2, a second support member is firmly attached to the crossmember, and an attaching member fixed to the fluid pressure-generating unit is supported by the second support member through an elastic member.

The invention according to claim 4 is characterized in that, in addition to the configuration of the invention according to any of claims 1 to 3, a shock absorber is provided between a swing arm which is swingably borne on the body frame while rotatably bearing a rear wheel and a link member which constitutes a part of a link mechanism provided between the swing arm and the body frame, and a sub-tank disposed on the rear side of the fluid pressure-generating unit so as to condition the damping force of the shock absorber is supported by the seat rail.

The invention according to claim 5 is characterized in that, in addition to the configuration of the invention according to claim 4, a sub-tank support member for supporting the sub-tank is fixed to the seat rail by co-fastening thereof together with a pillion step.

Incidentally, the brake pedal 16 in the embodiment below corresponds to the brake operating element in the present invention, the rear fluid pressure-generating unit 17R in the embodiment corresponds to the fluid pressure-generating unit in the invention, the rear pressure-regulating unit 18R in the embodiment corresponds to the pressure-regulating unit in the invention, the first pressure sensor 34 in the embodiment corresponds to the operating amount detector in the invention, the rubber bushing 156 in the embodiment corresponds to the elastic member in the invention, and the rear wheel brake BR in the embodiment corresponds to the wheel brake in the invention.

EFFECTS OF THE INVENTION

According to the invention of claim 1, the fluid pressure-generating unit is supported by the left-right pair of seat rails for supporting the riders' seat, and is laid out between both the seat rails in plan view. Therefore, the fluid pressure-generating unit can be arranged in a location which is close to the pressure-regulating unit disposed on the rear side of the engine body and in which a space necessary for installing the fluid pressure-generating unit is easy to secure.

In addition, according to the invention of claim 2 or 3, the fluid pressure-generating unit is floatingly supported by the first support member which is attached to one of both the seat rails and by the crossmember which connects both the seat rails to each other. Therefore, vibrations on the body frame side can be restrained from reaching the fluid pressure-generating unit.

According to the invention of claim 4, the fluid pressure-generating unit is arranged between the sub-tank and the engine body, whereby the fluid pressure-generating unit can be protected from external forces.

Furthermore, according to the invention of claim 5, the sub-tank support member is fixed to the seat rail by co-fastening thereof together with the pillion step, and, therefore, the number of component parts can be reduced.

For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the configuration of a brake system for a motorcycle.

FIG. 2 is a left side view of the motorcycle.

FIG. 3 is an exploded perspective view of a support structure for a front pressure unit.

FIG. 4 is a perspective view showing the condition where the front pressure-regulating unit is supported by support unit.

FIG. 5 is a side view showing the condition where the front pressure-regulating unit is supported on a body frame.

FIG. 6 is a plan view taken along arrow 6 of FIG. 5.

FIG. 7 is a sectional view taken along line 7-7 of FIG. 6.

FIG. 8 is a partly cut-away front view, as viewed along line 8-8 of FIG. 2, of the body frame, an engine body and front fluid pressure-generating unit.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 8.

FIG. 11 is a sectional view taken along line 11-11 of FIG. 9.

FIG. 12 is an enlarged sectional view taken along line 12-12 of FIG. 9.

FIG. 13 is an enlarged sectional view taken along line 13-13 of FIG. 9.

FIG. 14 is a view from the rear side of a rear pressure-regulating unit and the body frame.

FIG. 15 is a sectional view taken along line 15-15 of FIG. 14.

FIG. 16 is a sectional view taken along line 16-16 of FIG. 14.

FIG. 17 is an enlarged view of that portion of FIG. 2 which shows the rear fluid pressure-generating unit and the surroundings thereof.

FIG. 18 is a view taken along arrow 18 of FIG. 17.

FIG. 19 is a perspective view taken along arrow 19 of FIG. 17.

FIG. 20 is a perspective view taken along arrow 20 of FIG. 17.

FIG. 21 is a sectional view taken along line 21-21 of FIG. 18.

FIG. 22 is an enlarged view of that portion of FIG. 2 which shows a control unit and the vicinity thereof.

FIG. 23 is a view, corresponding to FIG. 22, showing the condition where a front cowl is removed.

FIG. 24 is a view showing the condition where the control unit is removed from the condition shown in FIG. 23.

FIG. 25 is a sectional view taken along line 25-25 of FIG. 22.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

An embodiment of the present invention will now be described, with reference to the drawings. Throughout this description, relative terms like “upper”, “lower”, “above”, “below”, “front”, “back”, and the like are used in reference to a vantage point of an operator of the vehicle, seated on the driver's seat and facing forward. It should be understood that these terms are used for purposes of illustration, and are not intended to limit the invention. Further, it should be noted that where a reference number is followed herein by multiple dots such as . . . , that is a short way of indicating that more than one of that referenced component is present in the assembled structure.

Now, a mode of carrying out the present invention will be described below, based on one embodiment of the invention shown in the attached drawings.

FIGS. 1 to 25 illustrate one embodiment of the present invention, in which FIG. 1 is a diagram showing the configuration of a brake system for a motorcycle; FIG. 2 is a left side view of the motorcycle; FIG. 3 is an explodes perspective view of a support structure for a front pressure-regulating unit; FIG. 4 is a perspective view showing the condition where the front pressure-regulating unit is supported by the support unit; FIG. 5 is a side view showing the condition of support of the front pressure-regulating unit on a body frame; FIG. 6 is a plan view taken along arrow 6 of FIG. 5; FIG. 7 is a sectional view taken along line 7-7 of FIG. 6; FIG. 8 is a partly cut-away front view, as viewed along line 8-8 of FIG. 2, of the body frame, an engine body and front fluid pressure-generating unit; FIG. 9 is a sectional view taken along line 9-9 of FIG. 8; FIG. 10 is a sectional view taken along line 10-10 of FIG. 8; FIG. 11 is a sectional view taken along line 11-11 of FIG. 9; FIG. 12 is an enlarged sectional view taken along line 12-12 of FIG. 9; FIG. 13 is an enlarged sectional view taken along line 13-13 of FIG. 9; FIG. 14 is a view from the rear side of a rear pressure-regulating unit and the body frame; FIG. 15 is a sectional view taken along line 15-15 of FIG. 14; FIG. 16 is a sectional view taken along line 16-16 of FIG. 14; FIG. 17 is an enlarged view of that portion of FIG. 2 which shows the rear fluid pressure-generating unit and the surroundings thereof; FIG. 18 is a view taken along arrow 18 of FIG. 17; FIG. 19 is a perspective view taken along arrow 19 of FIG. 17; FIG. 20 is a perspective view taken along arrow 20 of FIG. 17; FIG. 21 is a sectional view taken along line 21-21 of FIG. 18; FIG. 22 is an enlarged view of that portion of FIG. 2 which shows a control unit and the vicinity thereof; FIG. 23 is a view, corresponding to FIG. 22, showing the condition where a front cowl is removed; FIG. 24 is a view showing the condition where the control unit is removed from the condition shown in FIG. 23; and FIG. 25 is a sectional view taken along line 25-25 of FIG. 22.

First, in FIG. 1, a front wheel brake BF provided in a motorcycle is provided with a front pressure-regulating unit 18F by which a fluid pressure outputted from a front master cylinder MF according to an operation of a brake lever 15 serving as a brake operating element can be exerted and by which a fluid pressure outputted from front fluid pressure-generating unit 17F can also be exerted. The front pressure-regulating unit 18F is interposed between the front master cylinder MF and the front fluid pressure-generating unit 17F, and the front wheel brake BF. In addition, the rear wheel brake BR is provided with rear pressure-regulating unit 17R by which a fluid pressure outputted from a rear master cylinder MR according to an operation of a brake pedal 16 serving as a brake operating element can be exerted and by which a fluid pressure outputted from rear fluid pressure-generating unit 17R can also be exerted. The rear pressure-regulating unit 18R is interposed between the rear master cylinder MR and the rear fluid pressure-generating unit 17R, and the rear wheel brake BR.

The front fluid pressure-generating unit 17F, which generates a fluid pressure by operation of an electric motor 19, includes: the electric motor 19, a piston 22 slidably fitted in a cylinder body 20 while forming a fluid pressure chamber 21 between itself and the cylinder body 20; a return spring 23 disposed between the cylinder body 20 and the piston 22 so as to urge the piston 22 to the side for increasing the internal volume of the fluid pressure chamber 21; a pushing shaft 24 coaxially linked to the piston 22 from the side opposite to the fluid pressure chamber 21; and a gear mechanism 26 which has a gear 25 coaxially screw engaged with the pushing shaft 24 through a ball screw (not shown) and which is connected to an output shaft of the electric motor 19. The front fluid pressure-generating unit 17F can output, from the fluid pressure chamber 21, a fluid pressure varying according to the operation of the electric motor 19.

The rear fluid pressure-generating unit 17R is configured in the same fashion as the front fluid pressure-generating unit 17F above, and, therefore, it is only shown in the figure with its parts corresponding to those of the front fluid pressure-generating unit 17F being denoted by the same reference symbols as used above, and with detailed description thereof omitted.

The front pressure-regulating unit 18F includes: a first solenoid-operated on-off valve 28 for switching the communication/cutoff between the front master cylinder MF and the front wheel brake BF; a second solenoid-operated on-off valve 29 for switching the communication/cutoff between the front fluid pressure-generating unit 17F and the front wheel brake BF; a stroke simulator 30 for exerting a dummy reaction force according to the operating amount of the brake lever 15 on the front master cylinder MF when the first solenoid-operated on-off valve 28 is closed; a third solenoid-operated on-off valve 31 for switching the communication/cutoff between the stroke simulator 30 and the front master cylinder MF; a first one-way valve 32 connected in parallel to the second solenoid-operated on-off valve 29 so as to permit the flow of a brake fluid from the front fluid pressure-generating unit 17F to the side of the front wheel brake BF; and a second one-way valve 33 connected in parallel to the third solenoid-operated on-off valve 31 so as to permit the flow of the brake fluid from the stroke simulator 30 to the side of the front wheel brake BF. The pressure in the stroke simulator 30 is detected by a first pressure sensor 34 serving as operating amount detector, the output fluid pressure of the front master cylinder MF is detected by a second pressure sensor 35, and the output fluid pressure of the front fluid pressure-generating unit 17F is detected by a third pressure sensor 36.

The first pressure sensor 34 obtains the operating amount of the brake lever 15 by detecting the output fluid pressure of the front master cylinder MF when the first solenoid-operated on-off valve 28 is closed. The second pressure sensor 35 is provided for fail-safe diagnosis, and a judgment that an abnormal state is present can be made when a difference of not less than a predetermined value is generated between the pressure detected by the second pressure sensor 35 and the value detected by the first pressure sensor 34. In addition, the value detected by the third pressure sensor 36 is used in a fluid pressure feedback control for controlling the output fluid pressure of the front fluid pressure-generating unit 17F on the basis of the value detected by the first pressure sensor 34.

The first solenoid-operated on-off valve 28 is a normally open type solenoid valve, while the second and third solenoid-operated on-off valves 29, 31 are normally closed type solenoid on-off valves. The opening/closing operations of the first to third solenoid-operated on-off valves 28, 29, 31 and the operations of the electric motor 19 in the front fluid pressure-generating unit 17F are controlled by a control unit 39 connected with a battery 38. The control unit 39 is supplied as inputs with a value detected by a front speed sensor 40F and the values detected by the first to third pressure sensors 34, 35, 36. Based on the value detected by the front speed sensor 40F and the values detected by the first to third pressure sensors 34 to 36, the control unit 39 controls the opening/closing operations of the first to third solenoid-operated on-off valves 28, 29, 31 and the operation of the electric motor 19. In addition, an alarm lamp 41 is connected to the control unit 39.

At the ignition-ON times of the motorcycle, the first solenoid-operated on-off valve 28 is in the open state, whereas the second and third solenoid-operated on-off valves 29, 31 are in the closed state, the electric motor 19 is in the non-operative state, and the alarm lamp 41 is in the ON state. When the brake lever 15 is operated to cause a fluid pressure to be outputted from the front master cylinder MF under this condition, the fluid pressure is exerted on the front wheel brake BF through the first solenoid-operated on-off valve 28.

When running of the motorcycle is started, the control unit 39 performs an initial diagnosis, and turns OFF the alarm lamp 41 if the system is judged to be in normal condition. After the start of the running of the motorcycle, the system is put into a stand-by state, the third solenoid-operated on-off valve 31 is opened, and the front master cylinder MF is put into the state of communicating with the stroke simulator 30.

In response to the detection by the first pressure sensor 34 of a fluid pressure of not less than a predetermined value due to an operation of the brake lever 15 during the stand-by condition, the control unit 39 closes the first solenoid-operated on-off valve 28 and opens the second solenoid-operated on-off valve 29. Further, the control unit 39 operates the electric motor 19 of the front fluid pressure-generating unit 17F, to control the output fluid pressure of the front fluid pressure-generating unit 17F, which is detected by the third pressure sensor 36, in such a manner that the output fluid pressure of the front fluid pressure-generating unit 17F will be brought to a pressure according to the value detected by the first pressure sensor 34. This ensures that the front wheel brake BF is supplied with the fluid pressure outputted from the front fluid pressure-generating unit 17F according to the operational load on the brake lever 15.

The rear pressure-regulating unit 18R is configured in the same fashion as the front pressure-regulating unit 18F above, and, therefore, it is only shown in the figure with its parts corresponding to those of the front pressure-regulating unit 18F being denoted by the same reference symbols as used above, and with detailed description thereof omitted. Incidentally, in the fluid pressure control by the rear pressure-regulating unit 18R, the control unit 39 uses the value detected by the rear speed sensor 40R in place of the value detected by the front speed sensor 40F which is used in the fluid pressure control by the front pressure-regulating unit 18F.

In addition, by performing the fluid pressure control by the rear pressure-regulating unit 18R together with the fluid pressure control by the front pressure-regulating unit 18F according to the operation of the brake lever 15, the control unit 39 can carry out a rear braking force distribution control by which the front and rear wheel brakes BF, BR are operated so as to exert distributed braking forces on the front wheel and the rear wheel. In addition, on the contrary, by performing the fluid pressure control by the front pressure-regulating unit 18F together with the fluid pressure control by the rear pressure-regulating unit 18R in response to the operation of the brake pedal 16, the control unit 39 can carry out a rear braking force distribution control by which the front and rear wheel brakes BF, BR are operated so as to apply distributed braking forces to the front wheel and the rear wheel.

In FIG. 2, the body frame F of the motorcycle includes a head pipe 45, on which a front fork 43, and a steering handle 44 operatively connected to the front fork 43 are pivotally supported. The front fork rotatably supports the front wheel WF thereon, equipped with the front wheel brake BF.

The body frame F also includes a left-right pair of main frame sections 46 . . . extending rearwardly downwards from the head pipe 45; center frame sections 47 . . . connected respectively to corresponding rear parts of the main frame sections 46 . . . left and right pivot plates 48 . . . integrally connected to the center frame sections 47 . . . and extending downwards; and a left-right pair of seat rails 49 . . . respectively connected to rear parts of the center frame sections 47 . . . and extending rearwardly upwards.

The main frame sections 46 . . . are integrally provided with engine hangers 50 . . . extending downwards. An engine body 51 of an engine E of the in-line four-cylinder type, for example, is supported by lower parts of the engine hangers 50 . . . , the center frame sections 47 . . . and the pivot plates 48 . . . , in such an attitude that the cylinder axis thereof is inclined forwardly upwards.

The engine body 51 includes: a crankcase 53; a cylinder block 54 rising at a forwardly upward inclination from the crankcase 53; and a cylinder head 52 connected to an upper part of the cylinder block 54.

A fuel tank 55 is mounted on both the main frame sections 46 . . . on the upper side of the engine body 51. In addition, an upwardly extending intake system 57 is connected to a rear surface of the cylinder head 52 of the engine body 51, and an air cleaner 56 that the intake system 57 has at its upstream end is so disposed as to be covered with the fuel tank 55. On the other hand, an exhaust system 58 connected to a front surface of the cylinder head 52 includes: a plurality of exhaust pipes 59 . . . which are connected to the front surface of the cylinder head 52 in the manner of corresponding respectively to the cylinders and which extend downwards from the cylinder head 52; and an exhaust muffler 60 disposed between rear parts of both the seat rails 49 . . . in the state of being connected to the exhaust pipes 59 . . . . Moreover, the exhaust pipes 59 . . . have inclined parts 59 a extending forwardly downwards from the front surface of the cylinder head 52, and curved parts 59 b curved from lower parts of the inclined parts 59 a . . . toward the lower side of the engine body 51, so that a space triangular in shape in side view is formed between the exhaust pipes 59 and the front surface of the engine body 51. Furthermore, on the front side of the engine body 51, a radiator 61 is fixedly disposed so as to be located on the skew upper side of the exhaust pipes 59 . . . .

On the pivot plates 48 . . . of the body frame F, a front end part of a swing arm 62 rotatably supporting the rear wheel WR (which is equipped with the rear wheel brake BR) on its rear end parts is vertically swingably borne. A link mechanism 63 is provided between a front-end-side lower part of the swing arm 62 and lower parts of the pivot plates 48, and a lower end part of a shock absorber 65 connected at its upper end part to the swing arm 62 and extending vertically is connected to a link member 64 constituting a part of the link mechanism 63.

In addition, an output from a transmission (not shown) incorporated in the crankcase 53 possessed by the engine body 51 is transmitted to the rear wheel WR through chain-type power transmission unit 67 having an endless chain 66.

A riders' seat 68 is provided on the seat rails 49 . . . so as to be disposed on the rear side of the fuel tank 55. The riders' seat 68 includes a front seat 69 on which to seat the driver, and a rear seat 70 on which to seat the passenger and which is spaced to the rear side from the front seat 69. Pillion steps 71 on which to rest the feet of the passenger seated on the rear seat 70 are fastened to outside surfaces of intermediate parts of the seat rails 49 . . . .

A part of the body frame F and the engine E are covered with a front cowl 72 formed from a synthetic resin. The front cowl 72 includes a front cover part 73 for covering the head pipe 45 on the front side, and side covers 74 . . . which are in connection with the front cover 73 and which cover the engine body 51, the exhaust pipes 59 . . . of the exhaust system 58, and the radiator 61 on both lateral sides.

In the motorcycle as above, the front fluid pressure-generating unit 17F, the front pressure-regulating unit 18F, the rear fluid pressure-generating unit 17R, the rear pressure-regulating unit 18R and the control unit 39 are disposed in the vicinity of the engine E, i.e., in the vicinity of the center of the vehicle body.

Now, a structure for arrangement of the front fluid pressure-generating unit 17F, the front pressure-regulating unit 18F, the rear fluid pressure-generating unit 17R, the rear pressure-regulating unit 18R, and the control unit 39 in the motorcycle, and the operations and effects of the structure, will be sequentially described below.

Front Pressure-Regulating Unit 18F

An arrangement structure of the front pressure-regulating unit 18F will be described referring to FIGS. 3 to 7. First, in FIG. 3, the first solenoid-operated on-off valve 28, the second solenoid-operated on-off valve 29, the stroke simulator 30, the third solenoid-operated on-off valve 31, the first one-way valve 32, and the second one-way valve 33 which constitute the front pressure-regulating unit 18F are arranged on a base 77 formed in a rectangular parallelepiped, or box shape by casting of a light metal such as an aluminum alloy.

Projecting parts of the first solenoid-operated on-off valve 28, the second solenoid-operated on-off valve 29, the third solenoid-operated on-off valve 31, the first one-way valve 32 and the second one-way valve 33 which are projecting from the base 77 are covered by a synthetic resin-made cover 78 integrally provided with a coupler part 78 a. The first to third pressure sensors 34 to 36 are also arranged on the base 77, and projecting parts of the first to third pressure sensors 34 to 36 which are projecting from the base 77 are also covered with the cover 78.

Referring to FIGS. 4 to 7 also, the front pressure-regulating unit 18F is arranged in a position which is on the rear side of the intake system 57 being connected to the cylinder head 52 of the engine body 51 mounted on the body frame F and being extended upwards from the cylinder head 52 and which is between the engine body 51 and the fuel tank 55 disposed on the upper side of the engine body 51. The front pressure-regulating unit 18F is floatingly supported, through an elastic case 79 covering the pressure-regulating unit 18F, on support unit 83 supported on the body frame F.

The elastic case 79 includes lower and upper case members 80, 81 provided as bisected lower and upper parts so as to clamp the front pressure-regulating unit 18F in such an attitude as to have the base 77 located on the upper side. Both the case members 80, 81 are formed of an elastic material, for example, a rubber.

The lower case member 80 is formed in a box-like shape open to the upper side so that the cover 78 of the front pressure-regulating unit 18F can be fitted therein, and the upper case member 81 is formed in a box-like shape open to the lower side so that the base 77 of the front pressure-regulating unit 18F can be fitted therein. Moreover, the upper case member 81 is provided with a cutout 82 for permitting the coupler 78 a of the cover 78 to project therethrough. In addition, of both the case members 80 and 81, at least the lower case member 80 is integrally and projectingly provided at its inner surface, in this embodiment, both the case members 80 and 81 are integrally and projectingly provided at their inner surface, with a plurality of projections 80 a . . . , 81 a . . . put into the pressure-regulating unit 18F.

The support unit 83 is composed in a cage-like form by use of a lower cage body 84 which is attached to the body frame F so as to cover substantially the whole perimeter of a lower part of the front pressure-regulating unit 18F and to support the front pressure-regulating unit 18F on the lower side of the latter, and an upper cage body 85 which is fastened to the lower cage body 84.

The lower cage body 84 has a plurality of bent, small-width metallic plate materials connected to each other. Specifically, the lower cage body 84 includes: a cage part 84 a surrounding substantially the whole perimeter of the lower part of the front pressure-regulating unit 18F; two support plate parts 84 b, 84 c connected to the cage part 84 a so as to support the front pressure-regulating unit 18F on the lower side of the latter; three support arm parts 84 d, 84 e, 84 f extending outwardly sideways from the cage body 84 a; and two attaching projected parts 84 g, 84 h projected from the cage body 84 a so as to fasten the upper cage body 85 thereto.

The front pressure-regulating unit 18F, together with the lower case member 80 fitted in a lower part thereof, is fitted into and supported by the cage part 84 a and both the support plate parts 84 b, 84 c of the lower cage body 84.

The support arm parts 84 d, 84 e, 84 f are extended to the side of the left-side main frame section 46 and the left-side center frame section 47, of both the main frame sections 46 . . . and both the center frame sections 47 . . . of the body frame F. The support arm part 84 d is fastened to the engine hanger 50 integral with the main frame section 46 by a bolt 86, the support arm part 84 e is fastened to the main frame section 46 on the rear side relative to the engine hanger 50 by a bolt 87, and the support arm part 84 f is fastened to the center frame section 47 by a bolt 88.

The upper frame body 85 is brought from above into contact with the upper case member 81 fitted from above into an upper part, or the base 77, of the front pressure-regulating unit 18F, and is fastened to both the attaching projected parts 84 g, 84 h of the lower frame body 84. The upper frame body 85 integrally includes: a presser part 85 a put into contact with the upper case member 81 from above; and a pair of attaching leg parts 85 b, 85 c extended from the presser part 85 a toward the sides of both the attaching projected parts 84 g, 84 h.

On the other hand, weld nuts 89 . . . are firmly attached to the lower surfaces of both the attaching projected parts 84 g, 84 h of the lower frame body 84. Bolts 90, 90 passed through tip parts of both the attaching leg parts 85 b, 85 c and through both the attaching projected parts 84 g, 84 h are screw engaged with the weld nuts 89 . . . and tightened, whereby the upper frame body 85 is fastened to the lower frame body 84. As a result, the support unit 83 is composed in a frame form by use of the lower frame body 84 which is attached to the body frame F so as to cover substantially the whole perimeter of the lower part of the front pressure-regulating unit 18F and to support the front pressure-regulating unit 18F on the lower side of the latter, and the upper frame body 85 fastened to the lower frame body 84. In addition, the front pressure-regulating unit 18F is clamped between the lower frame body 84 and the upper frame body 85, with the lower case member 80 and the upper case member 81 (which are formed of an elastic material) interposed therebetween.

Moreover, the front pressure-regulating unit 18F is disposed on the upper side of and in proximity to a cooling pipe (not shown) constituting a part of a cooling water circulation circuit provided for the engine E. In view of this, the lower case member 80 is provided in its lower surface with a recessed part 80 b which is curved to the upper side in order to obviate interference with the cooling water pipe, whereby a cooling effect on the front pressure-regulating unit 18F owing to the arrangement of the unit in proximity to the cooling water pipe can be obtained.

According to the arrangement structure of the front pressure-regulating unit 18F as above, the front pressure-regulating unit 18F is covered by the elastic case 79, so that the influence of the heat from the engine E can be prevented from being exerted on the front pressure-regulating unit 18F. In addition, since the front pressure-regulating unit 18F is floatingly supported through the elastic case 79 on the support unit 83 supported on the body frame F, transmission of vibrations from the engine E to the front pressure-regulating unit 18F can be suppressed.

Moreover, the front pressure-regulating unit 18F is arranged in a position which is on the rear side of the intake system 57 being connected to the cylinder head 52 of the engine body 51 mounted on the body frame F and being extended upwards from the cylinder head 52 and which is between the engine body 51 and the fuel tank 55 disposed on the upper side of the engine body 51. This ensures that the front pressure-regulating unit 18F is disposed at such a position as to be less liable to be exposed to the radiant heat from the exhaust system 58 of the engine E, whereby the influence of the heat from the engine E upon the front pressure-regulating unit 18F can be effectively restrained. In addition, the front pressure-regulating unit 18F is laid out in a comparatively large vacant space on the rear side of the intake system 57, whereby the influence of the front pressure-regulating unit 18F upon the layout of other component parts can be minimized.

In addition, the elastic case 79 is composed of the elastic material-made lower and upper case members 80, 81 provided as bisected lower and upper parts so as to clamp the front pressure-regulating unit 18F from the lower and upper sides, and, at least the lower case member 80 of both the case members 80 and 81, in this embodiment, both of the case members 80 and 81 are integrally and projectingly provided at their inner surfaces with the plurality of projected parts 80 a . . . , 81 a . . . put into contact with the front pressure-regulating unit 18F. Therefore, the front pressure-regulating unit 18F can be floatingly supported assuredly while facilitating the operation of containing the front pressure-regulating unit 18F into the elastic case 79.

Furthermore, the front pressure-regulating unit 18F is floatingly supported, through the lower and upper case members 80 and 81 of the elastic case 79, on the support unit 83 mounted to the body frame F. In addition, the support unit 83 is composed in a frame form by use of the lower frame body 84 which is attached to the body frame F so as to cover substantially the whole perimeter of the lower part of the front pressure-regulating unit 18F and to support the front pressure-regulating unit 18F on the lower side of the latter, and the upper frame body 85 which is fastened to the lower frame body 84. Moreover, the front pressure-regulating unit 18F is clamped between the lower frame body 84 and the upper frame body 85, with the lower and upper case members 80 and 81 therebetween. Therefore, by a simple process in which the front pressure-regulating unit 18F is mounted to the lower frame body 84 attached to the body frame F through the lower case member 80 and then the upper frame body 85 with the upper case member 81 interposed between itself and the front pressure-regulating unit 18F is attached to the lower frame body 84, the front pressure-regulating unit 18F can be floatingly supported on the support unit 83 mounted to the body frame F. Thus, the mounting operation is facilitated.

Front Fluid Pressure-Generating Unit 17F

An arrangement structure of the front fluid pressure-generating unit 17F will be described referring to FIGS. 8 to 13. First, as shown in FIG. 2, the front fluid pressure-generating unit 17F is arranged between the engine body 51 and the exhaust pipes 59 . . . extended downwards from the front surface of the cylinder head 52 in the engine body 51. Moreover, the exhaust pipes 59 . . . include the inclined parts 59 a . . . which extends forwardly downwards from the front surface of the cylinder head 52, and the curved parts 59 b . . . which are curved from the lower parts of the inclined parts 59 a . . . toward the lower side of the engine body 51, in such a manner that a space rectangular in shape in side view is formed between themselves and the front surface of the engine body 51, with the front fluid pressure-generating unit 17F being arranged in the space. Furthermore, the front fluid pressure-generating unit 17F is arranged on the rear lower side of the radiator 61 which is supported on the body frame F on the front side of the engine body 51.

In FIG. 8, the front fluid pressure-generating unit 17F is supported, through support unit 93, on the engine hangers 50 . . . provided to be integral with the left-right pair of main frame sections 46 which extend rearwardly downwards from the head pipe 45 and which constitute a part of the body frame F. The support unit 93 is composed in a frame form by use of a first support frame 94 which is attached to the engine hangers 50 . . . and which extends in the left-right direction on the rear side of the front fluid pressure-generating unit 17F, and a second support frame 95 which is attached to the first support frame 94 in such a manner as to surround the front fluid pressure-generating unit 17F from the front side of the latter.

Referring to FIG. 9 also, a weld nut 96 is securely attached to the rear surface of an intermediate part in the width direction of the first support frame 94, and a weld nut 97 is secured to the rear surface of a tip part of a support arm part 94 a branched skewly downward from a left-side end part (in FIG. 8, a right-side end part) of the first support frame 94 as viewed from a person facing in the running (forward) direction of the motorcycle. One end part of the second support frame 95 is fastened to the intermediate part in the width direction of the first support frame 94 by a bolt 98 screw engaged with the weld nut 96, and the other end part of the second support frame 95 is firmly attached to the tip part of the support arm part 94 a of the first support frame 94 by a bolt 99 screw engaged with the weld nut 97.

Referring to FIG. 10 also, while the brackets 53 a . . . provided at the crankcase 53 of the engine body 51 are fastened to the engine hangers 50 . . . provided to be integral with the main frame sections 46 . . . through bolts 105, attaching members 102 . . . clamped between the brackets 53 a . . . and the engine hangers 50 . . . are co-fastened to the engine hangers 50 . . . together with the brackets 53 a . . . by the bolts 105.

On the other hand, both end parts of the first support frame 94 are fitted with rubber bushings 100, 100. Collars 101 . . . provided at their one-side ends with flange parts 101 a . . . projecting outwards are inserted in the rubber bushings 100 . . . , and the flange parts 101 a . . . are put in abutment on the attaching members 102 . . . . In addition, washers 103 . . . are put in contact with the other-side ends of the collars 101 . . . so that the collars 101 . . . are clamped between the washers 103 . . . and the attaching members 102 . . . , and bolts 104 . . . passed through the washer 103 . . . and the collars 101 . . . are screw engaged with the attaching members 102 . . . . Thus, both left and right end parts of the first support frame 94 of the support unit 93 are fastened to the engine hangers 50 . . . of the left-right pair of main frame sections 46 . . . , by co-fastening thereof together with the brackets 53 a . . . of the crankcase 53 in the engine body 51.

Referring to FIG. 11 also, an attaching arm 106 extending upwards is securely attached to an intermediate part in the left-right direction of the first support frame 94. A rubber bushing 107 is mounted to an upper end part of the attaching arm 106, and a collar 108 provided at its one end with a flange part 108 a projecting outwards is passed through the rubber bushing 107. On the other hand, the cylinder block 54 of the engine body 51 is provided with a support boss part 54 a for contact with the flange part 108 a. A washer 109 is put in contact with the other end of the collar 108 so as to clamp the collar 108 between itself and the support boss part 54 a, and a bolt 110 passed through the washer 109 and the collar 108 is screw engaged with the support boss part 54 a.

Referring to FIG. 12 also, a support bar 111 extending downwards is secured to an intermediate part in the left-right direction of the first support frame 94. The support bar 111 is fitted in a rubber bushing 112 mounted to the crankcase 53 of the engine body 51.

Thus, both the left and right end parts of the first support frame 94 of the support unit 93 are supported on the engine hangers 50 . . . of the main frame sections 46 . . . through the rubber bushings 100 . . . , and the intermediate part in the left-right direction of the first support frame 94 is supported on the engine body 51 through the rubber bushings 107, 112.

The front fluid pressure-generating unit 17F is elastically supported by the support member 93, and a support plate 116 opposed from the front side to a bracket 115 provided at a left side part of the front fluid pressure-generating unit 17F is firmly attached to the first support frame 94 of the support unit 93.

In FIG. 13, a rubber bushing 117 is mounted to the support plate 116, and a collar 118 provided at its one end with a flange part 118 a projecting outwards is passed through the rubber bushing 117 so that the flange part 118 a makes contact with the bracket 115. In addition, a washer 119 is put in contact with the other end of the collar 118 so as to clamp the collar 118 between itself and the bracket 115, and a bolt 120 passed through the washer 119 and the collar 118 is screw engaged with the bracket 115.

In addition, the second support frame 95 is provided with a support plate part 121 which is opposed to the front fluid pressure-generating unit 17F from the lower side, and a support plate 122 which is opposed to the front fluid pressure-generating unit 17F from the left side. Rubber bushings 123, 124 mounted to the support plate parts 121, 122 are attached to the front fluid pressure-generating unit 17F through bolts 125, 126 by use of the same structure as that shown in FIG. 13.

In short, the front fluid pressure-generating unit 17F is supported on the support unit 93 through the rubber bushings 117, 123, and 124.

According to the arrangement structure of the front fluid pressure-generating unit 17F as above, the front fluid pressure-generating unit 17F is arranged between the engine body 51 and the exhaust pipes 59 . . . extended downwards from the cylinder head 52. Therefore, the front fluid pressure-generating unit 17F can be laid out by utilizing effectively the vacant space which is on the front side of the engine body 51 and on the lower side of the exhaust pipes 59 . . . , whereby concentration of mass can be contrived. Moreover, although the heat from the exhaust pipes 59 . . . reaches the front fluid pressure-generating unit 17F, the running airflow generated by the running of the motorcycle comes into contact with the front fluid pressure-generating unit 17F, so that the temperature of the front fluid pressure-generating unit 17F can be prevented from rising excessively. In addition, since the support unit 93 for supporting the front fluid pressure-generating unit 17F is supported through the rubber bushings 100 . . . , 107, 112 on the engine body 51 and the engine hangers 50 . . . of the main frame sections 46 . . . constituting a part of the body frame F, transmission of vibrations from the engine E to the front fluid pressure-generating unit 17F can also be restrained.

In addition, the cylinder head 52 is connected to an upper part of the cylinder block 54 rising at a forwardly upward inclination from the crankcase 53. The exhaust pipes 59 . . . connected to the front surface of the cylinder head 52 have the inclined surfaces 59 a . . . extending forwardly downwards from the front surface of the cylinder head 52, and the curved parts 59 b . . . curved from the lower parts of the inclined parts 59 a . . . toward the lower side of the engine body 51, and a space triangular in shape in side view is formed between the exhaust pipes 59 . . . and the front surface of the engine body 51. Moreover, the front fluid pressure-generating unit 17F is laid out in the space. Therefore, since a comparatively large space can be secured between the exhaust pipes 59 . . . and the front surface of the engine body 51, the running airflow can easily flow in the surroundings of the front fluid pressure-generating unit 17F disposed in the space, and the temperature of the front fluid pressure-generating unit 17F can be effectively prevented from rising excessively.

In addition, both the left and right end parts of the first support frame 94 in the support unit 93 are supported on the engine hangers 50 . . . of the left-right pair of main frame sections 46 . . . through the rubber bushings 100 . . . , and the intermediate part in the left-right direction of the first support frame 94 is supported on the engine body 51 through the rubber bushings 107, 112, so that the front fluid pressure-generating unit 17F can be floatingly supported while enhancing the rigidity of the support unit 93.

In addition, since both the left and right end parts of the support unit 93 are fastened to the engine hangers 50 . . . of the main frame sections 46 . . . by co-fastening thereof together with the brackets 53 a . . . of the crankcase 53 of the engine body 51, a reduction in the number of component parts and a reduction in the number of working steps can be contrived.

In addition, the support unit 93 is composed in a frame form by use of the first support frame 94 which is attached to the engine hangers 50 . . . of the main frame sections 46 . . . and which extends in the left-right direction on the rear side of the front fluid pressure-generating unit 17F, and the second support frame 95 which is attached to the first support frame 94 in such a manner as to surround the front fluid pressure-generating unit 17F from the front side. Therefore, the front fluid pressure-generating unit 17F can be supported in such a manner that the front fluid pressure-generating unit 17F can easily receive the running airflow.

Furthermore, since the front fluid pressure-generating unit 17F is laid out on the rear lower side of the radiator 61 supported by the body frame F on the front side of the engine body 51, the front fluid pressure-generating unit 17F can be protected by the radiator 61 and the exhaust pipes 59 . . . from foreign matters such as flying stones coming from the front side.

Rear Pressure-Regulating Unit 18R

An arrangement structure of the rear pressure-regulating unit 18R will be described referring to FIGS. 2 and 14 to 16. First, as shown in FIG. 2, the rear pressure-regulating unit 18R is arranged on the rear side of the engine body 51 and between an upper end part of the shock absorber 65 and the engine body 51. The rear pressure-regulating unit 18R is supported by a support member 130, as shown in FIGS. 14 and 15.

The support member 130 includes: a support member main part 130 a which is arranged between both the center frame sections 47, 47 while having a part thereof opposed from above to the rear pressure-regulating unit 18R disposed on the lower side of a crossmember 131 with a base part 77 located on the rear side and with a cover 78 located on the front side; attaching arm parts 130 b, 130 c, 130 d extended from the support member main part 130 a so as to be opposed to both the center frame sections 47, 47 and the back surface of the crossmember 131; and a pair of support arm parts 130 e, 130 f drooping from the support member main part 130 a so as to be located on both the left and right sides of the rear pressure-regulating unit 18R.

Rubber bushings 132, 133, and 134 are mounted to tip parts of the attaching arm parts 130 b, 130 c, and 130 d. Collars 135, 136, and 137 provided at their one-side ends with flange parts 135 a, 136 a, and 137 a projecting outwards are passed through the rubber bushings 132 to 134 so that the flange parts 135 a to 137 a make contact with the center frame sections 47, 47 and the back surface of the crossmember 131. In addition, washers 138, 139, and 140 are put in contact with the other-side ends of the collars 135 to 137 so that the collars 135 to 137 are clamped between them and the center frame sections 47, 47 and the crossmember 131. Bolts 141, 142, and 143 passed through the washers 138 to 140 and the collars 135 to 137 are screw engaged with the center frame sections 47, 47 and the crossmember 131.

A frame member 145 is attached to an upper part of the base 77 of the rear pressure-regulating unit 18R by three bolts 146, 146, and 146, for example. The frame member 145 is disposed between the support member main part 130 a and both the support arm parts 130 e, 130 f of the support member 130, and the rear pressure-regulating unit 18R. Three portions of the frame member 147 are supported respectively on the support member main part 130 a and both the support arm parts 130 e, 130 f through rubber bushings 147 . . . . Specifically, the upper part of the rear pressure-regulating unit 18R is attached to the support member 130 through the rubber bushings 147 . . . so as to be suspended from the support member 130.

In FIG. 16, the rubber bushings 147 . . . are mounted respectively to the support member main part 130 a and both the support arm parts 130 e, 130 f of the support member 130, and weld nut 148 are securely attached to the frame member 145 in the manner of corresponding to the rubber bushings 147 . . . . In addition, collars 149 . . . provided at their one-side ends with flange parts 149 a projecting outwards are passed through the rubber bushings 147 . . . so that the flange parts 149 a . . . are clamped between them and the support member main part 130 a and both the support arm parts 130 e, 130 f. In addition, washers 150 . . . are put in contact with the other-side ends of the collars 149 . . . so that the collars 149 . . . are clamped between them and the support member main part 130 a and both the support arm parts 130 e, 130 f, and bolts 151 . . . passed through the washer 150 . . . and the collars 149 . . . are screw engaged with the weld nuts 148 . . . .

According to the arrangement structure of the rear pressure-regulating unit 18R as above, the support member 130 for supporting the rear pressure-regulating unit 18R is floatingly supported by the pair of center frame sections 47 . . . disposed on both the left and right sides of the engine body 51 and by the crossmember 131 for connecting the center frame section 47 . . . to each other on the rear side of the engine body 51 in such a manner as to constitute a part of the body frame F together with the center frame sections 47 . . . , through the rubber bushings 132, 133, and 134. Therefore, vibrations transmitted from the engine E can be prevented from reaching the rear wheel pressure-regulating unit 18R. Moreover, the rigidity of the support member 130 can be set to a level sufficient to hold the rear wheel pressure-regulating unit 18R, without being affected by the rigidity on the side of the body frame F, which makes it unnecessary to enhance the strength of the support member 130 more than required. Thus, reductions in weight and cost can be contrived.

In addition, since the upper part of the rear wheel pressure-regulating unit 18R is so attached as to be suspended from the support member 130, the position of the rear wheel pressure-regulating unit 18R in the width direction of the body frame F can easily be conditioned so as not to interfere with other component parts.

Further, the rear wheel pressure-regulating unit 18R is arranged between the engine body 51 and the upper end part of the shock absorber 95 provided between the swing arm 62 and the link member 64, which constitutes a part of the link mechanism 63 provided between the swing arm 62 and the body frame F. Therefore, the rear wheel pressure-regulating unit 18R can be effectively laid out in the space between the engine body 51 and the upper end part of the shock absorber 65. Moreover, the rear wheel pressure-regulating unit 18R can be protected by surrounding the left and right sides and the front and rear sides of the rear wheel pressure-regulating unit 18R with the body frame F, the engine body 51 and the shock absorber 65.

Rear Fluid Pressure-Generating Unit 17R

An arrangement structure of the rear fluid pressure-generating unit 17R will be described referring to FIGS. 17 to 21. First, as shown in FIGS. 17 and 18, the rear fluid pressure-generating unit 17R is supported on the left-right pair of seat rails 49 . . . constituting a part of the body frame F; in plan view, it is arranged between both the seat rails 49, 49 at a position nearer to the left-side seat rail 49 of both the seat rails 49 . . . .

Referring to FIGS. 19 and 20 also, a first support member 154 is attached to the left-side seat rail 49 of both the seat rails 49 . . . , and the rear fluid pressure-generating unit 17R is floatingly supported by the first support member 154 and a crossmember 155 for connection between both the seat rails 49 . . . , through rubber bushings 156 . . . .

Both end parts of the crossmember 155 are connected to the seat rails 49 . . . by pairs of bolts 157, 157 . . . . In addition, the first support member 154 is fastened to the left-side seat rail 49 by a pair of bolts 158, 158.

A second support member 159 is secured to the crossmember 155, and an attaching member 160 fixed to the rear fluid pressure-generating unit 17R is supported on the second support member 159 through a rubber bushing 156.

Referring to FIG. 21 also, the attaching member 160 is firmly attached to the cylinder body 20 of the rear fluid pressure-generating unit 17R by a pair of screw members 161, 161, and the rubber bushing 156 is mounted to the attaching member 160. In addition, a weld nut 162 is securely attached to the second support member 159 at a position corresponding to the rubber bushing 156. A collar 163 provided at its one end with a flange part 163 a projecting outwards is passed through the rubber bushing 156 so as to put the flange part 163 a in contact with the second support member 159. In addition, a washer 164 is put in contact with the other end of the collar 163 so as to clamp the collar 163 between itself and the second support member 159, and a bolt 165 passed through the washer 164 and the collar 163 is screw engaged with the weld nut 162.

In addition, a support plate part 154 a opposed to the rear fluid pressure-generating unit 17R from the outer side is provided at a front part of the first support member 154, and a support plate part 154 b opposed to the rear fluid pressure-generating unit 17R from the rear side is provided at a rear part of the first support member 154. The rubber bushings 156, 156 mounted respectively to these support plate parts 154 a, 154 b are attached to the rear fluid pressure-generating unit 17R with bolts 166, 167, by the same attaching structure as that described referring to FIG. 21 above.

Meanwhile, a sub-tank 168 for adjusting the damping force of the shock absorber 65, provided between the swing arm 62 and the link member 64 of the link mechanism 63, is arranged on the rear side of the rear fluid pressure-generating unit 17R. The sub-tank 168 is supported by the left-side seat rail 49.

Specifically, a sub-tank support member 169 for supporting the sub-tank 168 is fixed to the left-side seat rail 49. The sub-tank support member 169 is fixed to the left-side seat rail 49 with a pair of bolts 170, 170 by co-fastening thereof together with the pillion step 71.

According to the arrangement structure of the rear fluid pressure-generating unit 17R as above, the rear fluid pressure-generating unit 17R is supported by the left-right pair of seat rails 49, 49 in such a manner as to be laid out between both the seat rails 49 . . . in plan view. Therefore, the rear fluid pressure-generating unit 17R can be laid out in the vicinity of the rear pressure-regulating unit 18R, which is disposed on the rear side of the engine body 51, and in a place where it is easy to secure the space necessary for disposing the rear fluid pressure-generating unit 17R.

In addition, the rear fluid pressure-generating unit 17R is floatingly supported by the first support member 154 which is attached to the left-side seat rail 49 of both the seat rails 49 . . . and by the crossmember 155 for connection between both the seat rails 49 . . . , through the rubber bushings 156 . . . . Therefore, vibrations on the side of the body frame F can be restrained from reaching the rear fluid pressure-generating unit 17R.

In addition, the sub-tank 168 for adjusting the damping force of the shock absorber 65 is disposed on the rear side of the rear fluid pressure-generating unit 17R and is supported by the left-side seat rail 49. Therefore, it is possible to lay out the rear fluid pressure-generating unit 17R between the sub-tank 168 and the engine body 51, and thereby to protect the rear fluid pressure-generating unit 17R from external forces.

Furthermore, since the sub-tank support member 169 for supporting the sub-tank 168 is fixed to the left-side seat rail 49 by co-fastening thereof together with the pillion step 71, the number of component parts can be reduced.

Control Unit 39

An arrangement structure of the control unit 39 will be described referring to FIGS. 22 to 25. The control unit 39 is arranged on the left side of the engine body 51 mounted on the body frame F. Moreover, in order to enhance the property for “knee gripping” by the driver, the control unit 39 is disposed on the inner side relative to the vehicle body side ends of that portion of the motorcycle at which the vehicle width is the largest. The control unit 39 is contained in and supported by a synthetic resin-made control unit support case 171 interposed between the control unit 39 and the engine body 51, and is covered with the side cover part 74 constituting a part of the front cowl 72.

The control unit support case 171 is formed in a box-like shape opened on the side opposite to the engine body 51 so as to contain the control unit 39 on the side opposite to the engine body 51. Meanwhile, the front pressure-regulating unit 18F supported on the body frame F through the support unit 83 is arranged on the inner side relative to the control unit support case 171, and an upper part of the control unit support case 171 is attached to the support arm parts 84 e, 84 f possessed by the lower frame body 84 constituting a part of the support unit 83, by bolts 172, 173. Specifically, as clearly shown in FIG. 25, weld nuts 178 . . . are secured to the support arm parts 84 e, 84 f, and the bolts 172, 173 passed through the control unit support case 171 and the support arm parts 84 e, 84 f are screw engaged with the weld nuts 178 . . . .

Meanwhile, a crankcase cover 174 such as a generator cover is fastened to a left side surface of the crankcase 53 constituting a part of the engine body 51, by a plurality of bolts 175, 175 . . . . To a lower support member 176 which is co-fastened to the crankcase 53 together with the crankcase cover 174 by use of one of the bolts 175, 175 . . . , a lower part of the above-mentioned control unit support case 171 is attached by a pair of bolts 177, 177. Specifically, as clearly shown in FIG. 25, a pair of weld nuts 179 . . . are firmly attached to the lower support member 176, and the bolts 177 . . . passed through the control unit support case 171 and the lower support member 176 are screw engaged with the weld nuts 179 . . . .

The control unit 39 is contained in the control unit support case 171 with, for example, three elastic members 181 . . . interposed between itself and the control unit support case 171. The control unit 39 is supported on the control unit support case 171 through a fixing member 182 which is put in elastic contact with an outside surface of the control unit 39 along the front-rear direction of the body frame F and which is detachably attached to the control unit support case 171. The fixing member 182 may be, for example, an endlessly continuous rubber string, which is disengageably engaged with lock parts 182, 182 provided at the control unit support case 171 at positions on the front and rear sides of the control unit 39.

The control unit support case 171 is provided with a running airflow leading-in part 184 for permitting the running airflow to pass to the side of the control unit 39, the running airflow inlet port 184 being located on the lower front side of the control unit 39, and also with a running airflow leading-out part 185 for leading out the running airflow having passed through the lateral sides of the control unit 39, the running airflow leading-out part 185 being located on the upper rear side of the control unit 39.

The side cover part 74 of the front cowl 72 covers the control unit 39, with a cushion member 186 between itself and a lower part of the control unit support case 171. The side cover part 74 is provided with a running airflow intake port 187 at its portion corresponding to the running airflow leading-in part 184, and with running airflow exhaust ports 188, 189, and 190 at its portions corresponding to the running airflow leading-out part 185.

According to the arrangement structure of the control unit 39 as above, the control unit 39 arranged on a lateral side of the engine body 51 is contained in and supported by the control unit support case 171 interposed between the control unit 39 and the engine body 51. Therefore, direct reach of the heat from the engine body 51 to the control unit 39 can be avoided by the control unit support case 171 interposed between the control unit 39 and the engine body 51, while permitting the control unit 39 to be disposed in the vicinity of the engine body 51.

Moreover, the running airflow leading-in part 184 for permitting the running airflow to pass to the side of the control unit 39 is formed at a front part of the control unit support case 171, and the running airflow leading-out part 185 for leading out the running airflow having passed through the lateral sides of the control unit 39 is formed at a rear part of the control unit support case 171. Therefore, during running of the motorcycle, the running airflow can be caused to pass through the lateral sides of the control unit 39, thereby cooling the control unit 39.

In addition, an upper part of the control unit support case 171 is attached to the support arm parts 84 e, 84 f possessed by the support unit 39 for supporting the front pressure-regulating unit 18F on the body frame F. Therefore, the component parts and members for supporting the front pressure-regulating unit 18F and the control unit support case 171 onto the body frame F can be made to be suited to common use, which contributes to a reduction in the number of component parts.

In addition, a lower part of the control unit support case 171 is attached to the lower support member 176 which is co-fastened to the crankcase 53 together with the crankcase cover 174 fastened to one side of the crankcase. Therefore, the bolts 175 for fastening the lower support member 176 to the side of the crankcase 53 can be used in common to the fastening of the crankcase cover 174, which contributes to a reduction in the number of component parts.

In addition, the control unit 39 accompanied by the plurality of elastic members 181 . . . interposed between itself and the control unit support case 171 is supported on the control unit support case 171 by the fixing member 182 which is put in elastic contact with the outside surface of the control unit 39 along the front-rear direction of the body frame F and which is detachably attached to the control unit support case 171. Therefore, the fixing member 182 can be attached and detached easily, whereby maintainability of the control unit 39 can be enhanced.

Furthermore, the control unit 39 is covered with the side cover part 74 constituting a part of the front cowl 72, and the running airflow intake port 187 and the running airflow exhaust ports 188, 189, and 190 are provided at portions corresponding to the running airflow leading-in part 184 and the running airflow leading-out part 185 of the side cover part 74. Therefore, the running airflow can be introduced from the exterior into the running airflow leading-in part 184 and can be exhausted from the running airflow leading-out part 185, whereby performance of cooling the control unit 39 is maintained, and, at the same time, the control unit 39 is covered with the side cover part 74, whereby the control unit 39 can be protected from externally coming foreign matter, rainwater, etc.

While the embodiment of the present invention has been described above, the invention is not limited to the embodiment, and various design modifications are possible without departure from the invention as described in claims.

Although the present invention has been described herein with respect to a number of specific illustrative embodiments, the foregoing description is intended to illustrate, rather than to limit the invention. Those skilled in the art will realize that many modifications of the illustrative embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention. 

What is claimed is:
 1. A motorcycle comprising: a body frame comprising left and right seat rails which are spaced apart from one another and provided to support a seat thereon; an engine mounted on said body frame, said engine comprising an engine body; a wheel brake; a manually operable brake operating element which is fluidly connected to said wheel brake; and a brake-by wire system comprising: an operation amount detector for detecting an amount of force applied to the brake operating element; a fluid pressure-generating unit capable of generating a fluid pressure independently from an operation of said brake operating element, a pressure-regulating unit interposed between said fluid pressure-generating unit and a wheel brake for regulating an output fluid pressure of said fluid pressure-generating unit and applying the regulated fluid pressure to said wheel brake, and a control unit for controlling the operation of said pressure-regulating unit on the basis of a signal from said operating amount detector, said pressure-regulating unit being disposed on the rear side of said engine body, wherein as seen in a top plan view thereof, said fluid pressure-generating unit is disposed between and supported by said left and right seat rails.
 2. The motorcycle as set forth in claim 1, wherein said fluid pressure-generating unit is flexibly supported, through a flexibly resilient member, by a first support member which is attached to one of said seat rails, and by a crossmember which connects both said seat rails to each other.
 3. The motorcycle as set forth in claim 2, wherein a second support member is firmly attached to said crossmember, and an attaching member, fixed to said fluid pressure-generating unit, is supported by said second support member through a flexibly resilient member.
 4. The motorcycle as set forth in claim 3, further comprising: a swing arm which is pivotally attached to said body frame and is supported for reciprocal movement thereon; a rear wheel which is rotatably attached to said swing arm; a link mechanism provided between said swing arm and said body frame, said link mechanism comprising a link member; a shock absorber extending between said swing arm and said link member; and a sub-tank for conditioning a damping force of said shock absorber, said sub-tank disposed on the rear side of said fluid pressure-generating unit and supported by said seat rail.
 5. The motorcycle as set forth in claim 2, further comprising: a swing arm which is pivotally attached to said body frame and is supported for reciprocal movement thereon; a rear wheel which is rotatably attached to said swing arm; a link mechanism provided between said swing arm and said body frame, said link mechanism comprising a link member; a shock absorber extending between said swing arm and said link member; and a sub-tank for conditioning a damping force of said shock absorber, said sub-tank disposed on the rear side of said fluid pressure-generating unit and supported by said seat rail.
 6. The motorcycle as set forth in claim 1, further comprising: a swing arm which is pivotally attached to said body frame and is supported for reciprocal movement thereon; a rear wheel which is rotatably attached to said swing arm; a link mechanism provided between said swing arm and said body frame, said link mechanism comprising a link member; a shock absorber extending between said swing arm and said link member; and a sub-tank for conditioning a damping force of said shock absorber, said sub-tank disposed on the rear side of said fluid pressure-generating unit and supported by said seat rail.
 7. The motorcycle as set forth in claim 6, wherein a sub-tank support member for supporting said sub-tank is fixed to said seat rail by co-fastening together with a pillion step.
 8. A motorcycle comprising: a body frame comprising left and right seat rails which are spaced apart from one another and provided to support a seat thereon; an engine mounted on said body frame, said engine comprising an engine body; a wheel brake; a manually operable brake operating element which is fluidly connected to said wheel brake; and a brake-by wire system comprising: an operation amount detector for detecting an amount of force applied to the brake operating element; a fluid pressure-generating unit capable of generating a fluid pressure independently from an operation of said brake operating element, a pressure-regulating unit interposed between said fluid pressure-generating unit and a wheel brake for regulating an output fluid pressure of said fluid pressure-generating unit and applying the regulated fluid pressure to said wheel brake, and a control unit for controlling the operation of said pressure-regulating unit on the basis of a signal from said operating amount detector, said pressure-regulating unit being disposed on the rear side of said engine body, wherein as seen in a top plan view thereof, said fluid pressure-generating unit is disposed between and supported by said left and right seat rails; wherein said fluid pressure-generating unit is flexibly supported, through a flexibly resilient member, by a first support member which is attached to one of said seat rails, and by a crossmember which extends between and connects both said seat rails; and wherein a second support member is firmly attached to said crossmember, and an attaching member, fixed to said fluid pressure-generating unit, is supported by said second support member through a flexibly resilient member.
 9. The motorcycle as set forth in claim 8, further comprising: a swing arm which is pivotally attached to said body frame and is supported for reciprocal movement thereon; a rear wheel which is rotatably attached to said swing arm; a link mechanism provided between said swing arm and said body frame, said link mechanism comprising a link member; a shock absorber extending between said swing arm and said link member; and a sub-tank for conditioning a damping force of said shock absorber, said sub-tank disposed on the rear side of said fluid pressure-generating unit and supported by said seat rail.
 10. The motorcycle as set forth in claim 9, wherein a sub-tank support member for supporting said sub-tank is fixed to said seat rail by co-fastening together with a pillion step.
 11. A motorcycle comprising: a body frame comprising left and right seat rails which are spaced apart from one another and provided to support a seat thereon; an engine mounted on said body frame, said engine comprising an engine body; a wheel brake; a manually operable brake operating element which is fluidly connected to said wheel brake; a swing arm which is pivotally attached to said body frame and is supported for reciprocal movement thereon; a rear wheel which is rotatably attached to said swing arm; a link mechanism provided between said swing arm and said body frame, said link mechanism comprising a link member; a shock absorber extending between said swing arm and said link member; and a sub-tank for conditioning a damping force of said shock absorber, said sub-tank disposed on the rear side of said fluid pressure-generating unit and supported by said seat rail; and a brake-by wire system comprising: an operation amount detector for detecting an amount of force applied to the brake operating element; a fluid pressure-generating unit capable of generating a fluid pressure independently from an operation of said brake operating element, a pressure-regulating unit interposed between said fluid pressure-generating unit and a wheel brake for regulating an output fluid pressure of said fluid pressure-generating unit and applying the regulated fluid pressure to said wheel brake, and a control unit for controlling the operation of said pressure-regulating unit on the basis of a signal from said operating amount detector, said pressure-regulating unit being disposed on the rear side of said engine body, wherein as seen in a top plan view thereof, said fluid pressure-generating unit is disposed between and supported by said left and right seat rails.
 12. The motorcycle as set forth in claim 11, wherein said fluid pressure-generating unit is flexibly supported, through a flexibly resilient member, by a first support member which is attached to one of said seat rails, and by a crossmember which connects both said seat rails to each other.
 13. The motorcycle as set forth in claim 12, wherein a second support member is firmly attached to said crossmember, and an attaching member, fixed to said fluid pressure-generating unit, is supported by said second support member through a flexibly resilient member.
 14. The motorcycle as set forth in claim 11, wherein a sub-tank support member for supporting said sub-tank is fixed to said seat rail by co-fastening together with a pillion step. 